This invention deals with perpetual calendar means which allow the user to determine the day of the week of any date requiring only minimal calculations while dealing with a few simple tables. Such determination may be undertaken for the modern Gregorian calendar as well as for the Julian, Islamic, Coptic or Zodiacal calendars.
Many so-called perpetual calendar schemes have been proposed in the past, however, such calendars usually include numerous and cumbersome tables or complicated calculations or combinations thereof. Typical calendar systems may be found in the references of interest discussed below, namely
U.S. Pat. No. 505,901 Oct. 3, 1893 (Hoyt) describes a calendar with rather large and confusing tables covering only a limited number of years.
U.S. Pat. No. 773,669 Nov. 1, 1904 (O'Shaughnessy) teaches a perpetual calendar requiring five large tables with an array of numerals and names of months and days in a color scheme arranged in a confusing manner.
U.S. Pat. No. 1,016,370 Feb. 6, 1912 (Singh) discloses a circular calendar using numbers arranged in a seemingly irregular fashion and color schemes. Although it encompasses the Gregorian and Julian calendars, no provisions are made for dates before B.C. or for Coptic, Islamic or Zodiacal calendars.
U.S. Pat. No. 1,374,532 Apr. 12, 1921 (Spillman) deals with a perpetual calendar applicable to the Julian and Gregorian systems, however, this calendar is limited to a time span from the 16th to the 20th century. No mention is made of Coptic, Islamic etc. calendars.
U.S. Pat. No. 1,608,411 Nov. 23, 1926 (Mateju) is concerned with a perpetual Gregorian calendar having cumbersome charts with a multiplicity of numbers in different colors running from 0 to 99. Julian, Islamic and other calendar notations cannot be determined.
Other background references of interest include U.S. Pat. Nos. 458,970 (Fitch); 789,166 (Manfred); 1,153,926 (Johnston); 2,588,795 (Bauer); 2,768,459 (Corbett); 2,788,595 (Edwards); 3,698,113 (Spicer); 3,792,541 (Engle); 3,936,966 (Zeiske); 4,251,935 (Wright); 4,285,147 and 4,285,148 (Kolar); 4,381,614 (Kebe) and 4,472,893 (Curti).
None of these references provide a date determining means and method as comprehensive yet facile to use as the instant invention.